Treated wood is lumber that has been chemically treated to resist decay, insects, and other environmental factors. This process typically involves soaking the wood in preservatives, which helps extend its lifespan, making it suitable for outdoor use in structures like decks, fences, and playgrounds. Common preservatives used in treated wood include chromated copper arsenate (CCA) and alkaline copper quaternary (ACQ). Treated wood is often marked with a stamp indicating its treatment level, ensuring consumers can choose the right type for their specific needs. Proper handling and disposal are important, as some treatments can be harmful to health and the environment.